In France, schools tend to teach French grammar and language right through to the end of secondary school. It’s a complicated language so this doesn’t surprise me. What has surprised me is seeing this advertisement for a duty free shop in England with graffiti to correct the poor grammar. Actually, the Oxford Dictionary says “compared to” is interchangeable these days, but even my boss is a stickler for “compared with”, and at least one other person agrees with him.
Whilst most graffiti writers struggle to spell correctly (as pointed out by Crap Graffiti), here we have the opposite: someone angry that the rule of grammar they probably learnt at school has not been adhered to. So, big points to the English(?) person who made this correction, whether the Oxford Dictionary agrees with you or not.